The invention relates to head rest arrangement for a motor vehicle seat.
A head rest arrangement of this kind comprises by way of example a backrest frame for a backrest of the motor vehicle seat which extends along a longitudinal direction of the backrest and serves to support the back of an occupant seated on the corresponding vehicle seat; an upper edge of the backrest frame which defines the backrest frame at the top in the upright function position; a head rest which can be fixed in at least one useful position above the upper edge of the backrest frame and whose head rest body has a front side provided for supporting the head of a vehicle occupant; a device for moving the head rest in the event of a crash in order to move the head rest body relative to the backrest frame upwards and/or forwards into a predeterminable position different from the useful position behind the head of a vehicle occupant and thus achieve an improved support of the head and neck area of the vehicle occupant in the event of a crash; as well as a locking device which counteracts displacement of the head rest and which can be unlocked in a crash situation.
By useful position of the head rest is meant a position which serves in normal operation of a motor vehicle to support the head of a vehicle occupant. With a head rest which can be adjusted in height relative to the top edge of the backrest such a useful position can be set for example by the occupant himself or alternatively can be set automatically through an occupant identification system which identifies a vehicle occupant from his weight, from a previously set seat longitudinal position or in some other way and then triggers the setting of a specific useful position of the head rest.
By crash situation is generally meant here a sudden occurrence of a (positive or negative) acceleration (more particularly a sharp vehicle deceleration) which goes beyond that which is to be expected during normal use of the vehicle in traffic. The threshold from which a displacement of the head rest from its function position is triggered conditioned by the crash is to be selected so that those actions on the vehicle and thus also on the vehicle occupants in which the head and neck region of the vehicle occupant can be exposed to particular stresses are detected. This can be determined through corresponding crash tests.
A displacement of the head rest from its useful position means thereby a change in the position of the head rest compared with the useful position into which the head rest had been previously brought for supporting the head of a vehicle occupant. This displacement is only then triggered when a vehicle deceleration suggesting a special strain on the head or neck region or some other extraordinary (possibly future) effect on the vehicle has been detected for example by a sensor. For this in particular an acceleration sensor or a proximity sensor (pre-crash sensor) is particularly suitable. This sensor need not necessarily be associated directly with the head rest arrangement itself but for this a sensor can be used which is present in any case for detection of a crash situation and for triggering an airbag device or some other safety device.
By upright function position of the backrest frame is presently meant a position of the backrest frame in which it extends—in relation to the state of the corresponding vehicle seat installed in a motor vehicle—substantially along the vertical vehicle axis. By backrest longitudinal direction of the backrest frame is meant that direction along which extends the spinal column of an occupant seated upright on the corresponding vehicle seat. If the backrest frame is located in its upright function position then the backrest longitudinal direction runs substantially along the vertical vehicle axis.
A head rest arrangement of the type mentioned at the beginning is known from the German Patent 100 51 344 C1. With this arrangement the head rest swivels about an imaginary (virtual) horizontal axis upwards and forwards in the direction of the head of an occupant located on the corresponding vehicle seat in order to ensure improved support of the head and neck region of the vehicle occupant.
The object of the invention is to improve a head rest arrangement of the type mentioned at the beginning.